The present invention relates to a hydraulic pressure booster cylinder which maximizes advantages and functions of a pneumatic cylinder and a hydraulic cylinder, and more particularly, the present invention relates to a hydraulic pressure booster cylinder which is capable of being quickly actuated to conduct a low pressure stroke under a low load situation and being automatically converted to a high pressure stroke conducting mode under a high load situation.
Generally, in a pneumatic cylinder or a hydraulic cylinder which is well known in the art, when a piston is repeatedly moved so as to perform a specific work, the same pressure is applied to the piston all the way. That is to say, due to the fact that the same pressure is applied to the piston under a low load situation prior to undertaking a regular work as well as under a high load situation after undertaking the work, a moving velocity of the piston is slow at an initial operating stage, and, when the work is undertaken or a load is imposed on the piston, since the moving velocity of the piston is further slowed, working efficiency cannot but be deteriorated.
Therefore, it would be desirable for a pneumatic or hydraulic cylinder to be actuated in such a way as to conduct a low pressure stroke with a low load applied before a work is initially undertaken and at the same time a high pressure stroke with a high load applied after the work is undertaken. In this connection, the present invention is directed toward a hydraulic pressure booster which can be quickly actuated upon conducting a low pressure stroke and can generate great working force upon conducting a high pressure stroke.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a hydraulic pressure booster cylinder which is capable of being quickly actuated to conduct a low pressure stroke under a low load situation and being automatically converted to a high pressure stroke conducting mode under a high load situation, thereby to output force of a desired level as occasion demands.
In order to achieve the above object, according to the present invention, there is provided a hydraulic pressure booster cylinder including a cylinder case possessing a first cylinder hole of a first inner diameter, a second cylinder hole of a second inner diameter equal to or less than the first inner diameter and a bore of a third inner diameter less than the second inner diameter, the bore being defined between the first cylinder hole and the second cylinder hole in a manner such that the first cylinder hole, second cylinder hole and bore are communicated one with another, a first piston reciprocatingly disposed in the first cylinder hole and having a trunk piston portion which is selectively inserted into the bore, a second piston reciprocatingly disposed in the first cylinder hole, the trunk piston portion of the first piston passing through the second piston, a first spring arranged between the first piston and the second piston to elastically support the second piston, a third piston reciprocatingly disposed in the second cylinder hole and having a piston rod which projects out of one end of the cylinder case, a slide piston reciprocatingly disposed in the second cylinder hole, the piston rod of the third piston passing through the slide piston, and a second spring arranged between the third piston and the slide piston, the hydraulic pressure booster cylinder taking first and second pneumatic chambers defined at the other end of the cylinder case and respectively connected to first and second pneumatic lines, a third pneumatic chamber defined between the third piston and the slide piston and connected to a third pneumatic line which is communicated with the outside, and a fourth pneumatic chamber defined between the slide piston and a cylinder cap which closes the one end of the cylinder case and connected to a fourth pneumatic line, characterized in that the slide piston is elastically supported by the second spring on the third piston, and a check valve which is elastically supported by a third spring, is driven by movement of the slide piston, wherein, upon conducting a low pressure stroke, when the piston rod of the third piston is retracted into the cylinder case, the slide piston is positioned close to the third piston while compressing the second spring, and when the piston of the third piston is extended out of the cylinder case, in the case of a low load situation, as compressed air is supplied into the second pneumatic chamber via the second pneumatic line, the second piston is moved toward the bore, and thereby the third piston and the slide piston are correspondingly moved to allow the piston rod of the third piston to extend out of the cylinder case, and wherein, upon conducting a high pressure stroke, when movement of the second piston is blocked by resistant force acting against the piston rod of the third piston, the slide piston is continuously moved toward the check valve by elastic force of the second spring and pushes the check valve in one direction, compressed air flows through the first pneumatic line into the first pneumatic chamber and air existing in the second pneumatic chamber is discharged to the outside, and, by movement of the first piston, the trunk piston portion of the first piston is moved toward the third piston through the bore while maintaining airtightness.